LED lamps are becoming more common. One known disadvantage is the fact that LED lamps can cause electromagnetic disturbances. The reason for these disturbances is mostly the power source of the LED lamp which power source is nowadays nearly always a step down switching power supply. The power source in question breaks fast mains voltage (about 320-340V) which is rectified with a diode bridge and filtered with capacitors mostly at the frequency of 50 kHz-500 kHz. This causes a strong electromagnetic radiation to the environment which radiation typically disturbs the listening of radio and watching of TV programmes. In the worst cases the power sources disturb even each other's functioning. In addition to this the input current and the input voltage have various phases in the power source in question which causes unpaired harmonic waves to the electrical network which harmonic waves disturb the functioning of other devices that are connected to the electrical network.